Stabilization of the SARS-CoV-2 receptor binding domain by protein core redesign and deep mutational scanning

Study aims to stabilize the SARS-CoV-2 receptor binding domain (RBD) by making mutations solely to amino acid residues inside the protein core. For deep mutational scanning, a site-saturation mutagenesis library of 90 positions in the RBD core was screened for binding against ACE2 tagged with the fluorophore PE. Displayed libraries were treated with 0 to 4000 U/ml chymotrypsin before binding ACE2, and for all libraries cells with a PE signal over 2000 were collected for sequencing. Mutations that are enriched in the chymotrypsin-treated libraries compared to the untreated reference libraries are predicted to be stabilizing.